WO2015107116A1 - Miroir euv et système optique à miroir euv - Google Patents

Miroir euv et système optique à miroir euv Download PDF

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Publication number
WO2015107116A1
WO2015107116A1 PCT/EP2015/050687 EP2015050687W WO2015107116A1 WO 2015107116 A1 WO2015107116 A1 WO 2015107116A1 EP 2015050687 W EP2015050687 W EP 2015050687W WO 2015107116 A1 WO2015107116 A1 WO 2015107116A1
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Prior art keywords
layer
group
thickness
thicknesses
layer thickness
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PCT/EP2015/050687
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German (de)
English (en)
Inventor
Thomas Schicketanz
Oliver Dier
Sebastian Strobel
Ralf Winter
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Carl Zeiss Smt Gmbh
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Application filed by Carl Zeiss Smt Gmbh filed Critical Carl Zeiss Smt Gmbh
Priority to JP2016564397A priority Critical patent/JP6527883B2/ja
Publication of WO2015107116A1 publication Critical patent/WO2015107116A1/fr
Priority to US15/215,123 priority patent/US10203435B2/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G02B5/0891—Ultraviolet [UV] mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G02B5/0816—Multilayer mirrors, i.e. having two or more reflecting layers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/08—Mirrors
    • G02B5/0816—Multilayer mirrors, i.e. having two or more reflecting layers
    • G02B5/085—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal
    • G02B5/0875—Multilayer mirrors, i.e. having two or more reflecting layers at least one of the reflecting layers comprising metal the reflecting layers comprising two or more metallic layers
    • G—PHYSICS
    • G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
    • G21K—TECHNIQUES FOR HANDLING PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES
    • G21K1/00—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating
    • G21K1/06—Arrangements for handling particles or ionising radiation, e.g. focusing or moderating using diffraction, refraction or reflection, e.g. monochromators
    • G21K1/062—Devices having a multilayer structure

Definitions

  • the invention relates to an EUV mirror according to the preamble of claim 1 and to an optical system having an EUV mirror according to the preamble of claim 16.
  • a preferred field of application is EUV microlithography.
  • Other applications include EUV microscopy and EUV mask metrology.
  • Masks for microlithography are nowadays predominantly microlithographic projection exposure methods.
  • masks (reticles) or other pattern-generating devices are used which carry or form the pattern of a structure to be imaged, e.g. a line pattern of a layer (layer) of a semiconductor device.
  • the pattern is positioned in a projection exposure apparatus between a lighting system and a projection lens in the region of the object plane of the projection lens and illuminated with an illumination radiation provided by the illumination system.
  • the radiation changed by the pattern passes through the projection objective as projection radiation, which images the pattern onto the substrate to be exposed, coated with a radiation-sensitive layer whose surface lies in the image plane of the projection objective that is optically conjugate to the object plane.
  • optical systems In order to be able to produce ever finer structures, optical systems have been developed in recent years which operate at moderate numerical apertures and achieve high resolving power essentially by the short wavelength of the electromagnetic radiation from the extreme ultraviolet range (EUV) used, in particular at working wavelengths in the range between 5 nm and 30 nm.
  • EUV extreme ultraviolet range
  • EUV lithography Radiation from the extreme ultraviolet range can not be focused or guided by refractive optical elements because the short wavelengths are absorbed by the known optical materials transparent at higher wavelengths. Therefore, mirror systems are used for EUV lithography.
  • a class of EUV mirrors operates at relatively high incidence angles of the incident radiation, that is, grazing incidence (grazing incidence). cidence) according to the principle of total reflection.
  • multi-layer mirrors are used for vertical or almost vertical incidence of radiation.
  • Such a mirror (EUV mirror) which has a reflective effect on radiation from the EUV region, has a substrate on which is applied a multilayer multilayer coating which has a reflective effect for radiation from the extreme ultraviolet region (EUV) and has many layer pairs having alternating low refractive and high refractive layer material.
  • Layer pairs for EUV mirrors are often built up with the layer material combinations molybdenum / silicon (Mo / Si) or ruthenium / silicon (Ru / Si).
  • the reflectivity or reflectivity of multilayer mirrors depends strongly on the angle of incidence and on the wavelength of the incident EUV radiation.
  • a high maximum value of the reflectivity can be achieved if the multi-layer arrangement consists essentially of a periodic layer sequence with a multiplicity of identical layer pairs.
  • a relatively small half width (fill width at half maximum, FWH M) of the reflectivity curve then results.
  • the multi-layer arrangement comprises a plurality of layer groups, each of which has a periodic sequence of at least two individual layers of different materials forming a period The number of periods and the thickness of the periods of the individual layer groups decrease from the substrate to the surface
  • An exemplary embodiment has three different layer groups: This layer structure is intended to ensure that, on the one hand, the peak wavelengths of the reflection maxima of the respective layer groups are shifted from the substrate to the surface towards shorter wavelengths, so that a broader reflection peak can be achieved by superposing the reflection of the individual layer groups of the whole ystems is generated.
  • all layer groups can be approximately equal to the reflectivity of the contribute to the overall system. In this way, a nearly constant reflectivity over a large wavelength range or angle range
  • EUV mirrors with aperiodic multi-layer arrangement are also known from WO 2009/043374 A1.
  • the multi-layer arrangement has a protective layer ("capping layer") on the radiation entrance side.
  • the layer thicknesses of individual layers vary chaotically in at least one subregion of the multilayer layer arrangement.
  • Wideband EUV mirrors for vertical or nearly vertical incidence of radiation are known from the prior art, which have a multi-layer arrangement with different groups of layer pairs.
  • a near-surface layer group (surface layer film group) is arranged on the radiation entrance side of the multi-layer layer arrangement. Opposite the radiation entrance side follows an additional layer (additional layer). This is followed by a deeper group of layer pairs (deep layer film group) in the direction of the substrate.
  • the reflectivity of the near-surface layer group is higher than the reflectivity of the substrate near deeper layer group and the reflected radiation is phase-shifted due to the presence of the additional layer so that a Reflektellessmaximum value (reflectivity peak value) of the entire multi-layer layer arrangement is lower and the reflectivity to the peak wavelength is higher than in the absence of the additional layer.
  • the optical layer thickness of the additional layer should correspond to approximately one quarter of the wavelength of the EUV radiation (ie ⁇ / 4) or half the period thickness of the multi-layer layer arrangement or this value plus an integral multiple of the period thickness.
  • the invention provides an EUV mirror having the features of claim 1. Furthermore, an optical system with an EUV mirror having the features of claim 16 is provided. Advantageous developments are specified in the dependent claims. The wording of all claims is incorporated herein by reference.
  • the first layer group has a sufficiently high number of first layer pairs which together form a plurality of interfaces between relatively high refractive and relatively low refractive layer material, which each reflect a portion of the incident EUV radiation, so that the first layer group acts in total for the radiation reflective and makes a substantial contribution to the overall reflectivity of the multi-layer arrangement.
  • the first group of layers has at least ten first pairs of layers. It is also possible for considerably more than ten first layer pairs to be provided, for example 15 or more, or 20 or more, or 30 or more, or 50 or more first layer pairs.
  • a pair of layers each comprise a first layer of a relatively high-refractive layer material and a second layer of a relatively low-refractive layer material.
  • Such layer pairs are also referred to as "period", “double layer” or “bilayer” and can be characterized by a period thickness, which in this application corresponds to the sum of the (geometrical or optical) layer thicknesses of all layers of a first layer pair to the two layers of relatively high refractive or relatively low refractive layer material still have one or more further layers, for example, an intermediate barrier layer to reduce the interdiffusion between adjacent layers.
  • the nominal layer thicknesses of one of the layer materials are definable by a single monotonous first layer thickness function as a function of the period number, while the layer thicknesses of the other of the layer materials (second layer material or first layer material) depend on the period number according to a second Schichtdickenverlaufsfunktion varies.
  • Period number here refers to a numbering of the immediately consecutive periods or pairs of layers starting on the side facing the substrate and ending at the radiation entrance side of the first group of layers.
  • the period number can also be referred to as a layer pair number
  • the nominal layer thicknesses of the individual layers The actual layer thicknesses do not have to correspond to the mathematically exact function values of the layer thickness progression function (ie, the nominal layer thicknesses) of the layer thickness profile function of the respective layer (period number or layer pair number)
  • the actual layer thicknesses may rather deviate within the scope of manufacturing tolerances from the functional value resulting from the respective layer thickness profile function. Manufacturing tolerances can be for each individual layer, for example in the range of 5% or at most 10% of the absolute layer thickness of the single layer.
  • the (nominal) layer thicknesses follow a simply monotonous first layer thickness profile function.
  • the layer thicknesses which follow the monotonous first Schichtdickenverlaufsfunktion thus do not vary arbitrarily or in a complicated way, but follow a certain, relatively easy parametrisierbaren systematics. For example, such a system makes it easier to deduce manufacturing errors from measurements. Furthermore, for example, the layer roughness of a layer can be better adjusted and / or controlled if the layer thickness of this layer material follows a monotonous first layer thickness profile function.
  • a coating system can change over time during the entire coating process, that is to say during the production of the successive individual layers of a multilayer coating arrangement, with regard to a number of properties relevant to the coating result.
  • This normally makes it difficult to deduce the film thicknesses of the individual layers from the results of measurements, for example reflectivity measurements.
  • a linear error of the layer thickness results, so that the size of the error depends on the design layer thickness (ie the nominal layer thickness).
  • a linear drift of the individual layer thicknesses may occur due to changes in the coating system during the coating, so that, for example, instead of a layer thickness of a selected layer material that is constant over many layer pairs, a gradual increase or decrease in the layer thicknesses of this layer material increases with increasing distance from the substrate results.
  • the first layer thickness function is a linear function, then these two effects need not be determined separately so that it is possible to more easily interpret the results of the measurements. If, on the other hand, the nominal layer thicknesses did not follow a monotonous layer thickness progression function, then both errors would have to be known separately in order to be able to determine the correct layer thicknesses.
  • the layer thickness of the other layer material should vary depending on the layer pair number according to a second Schichtdickenverlaufsfunktion, so that result for this other layer material within the first layer group differences in layer thickness, which are well outside the manufacturing tolerances.
  • the first layer thickness profile function is completely definable by one, two or three layer thickness parameters. If this condition is met, a maximum of three layer thickness parameters is sufficient to completely define the values of the nominal layer thicknesses of one of the layer materials over the entire first layer group. This results in a very simple description of the layer thicknesses concerned and a correspondingly simple and precise possibility of interpreting Measurement results, for example, to infer uncontrollable changes in the coating process.
  • the first layer thickness progression function is a constant function such that the layer thicknesses of one of the layer materials over the entire first layer group are constant (within tolerances).
  • the layer material which is to be produced within the first layer group with a constant layer thickness may be a relatively high-breaking first layer material or a relatively low-breaking second layer material.
  • the layer material produced according to a constant first layer thickness function is selected from the group consisting of molybdenum (Mo), ruthenium (Ru), rhodium (Rh), and palladium (Pd).
  • the second layer thickness profile function defines a stochastic layer thickness distribution of the other layer material.
  • This other layer material may be, for example, silicon (Si).
  • the layer stress can be predicted even with very different layer thicknesses.
  • the first layer thickness function is a linearly increasing or decreasing function so that the layer thicknesses of one of the layer materials increase or decrease linearly over the entire first layer group. In these cases, the specification of two layer thickness parameters is sufficient to completely determine the nominal layer thicknesses of the layer material concerned.
  • the gradient or the slope indicates the amount by which the layer thicknesses of immediately adjacent layers of the same layer material differ.
  • the first layer thickness profile function is a linearly increasing or linearly decreasing function
  • the second layer thickness profile function is also a linearly increasing or linearly decreasing function.
  • the second Schichtdickenverlaufsfunktion runs in opposite directions to the first Schichtdickenverlaufsfunktion, so that, for example, with linearly decreasing layer thickness of the first layer material, the layer thickness of the second layer material increases linearly or vice versa.
  • the period thickness within the first layer group it is possible for the period thickness within the first layer group to remain constant or to vary only slightly, ie, less than the individual layer thicknesses.
  • the layer thicknesses of both layer materials equally fall off linearly or equally increase linearly, wherein the gradients for the individual layer materials may be the same or different. In these cases, the period thickness will also increase or decrease linearly.
  • the first layer thickness function is a quadratic or an exponential function such that a gradual increase or a gradual decrease in the layer thickness of the affected layer material results in small systematic steps within the first layer group, and in addition the step size, ie Layer thickness difference between immediately adjacent layers of the same layer material increases or decreases with increasing distance from the substrate.
  • the second layer thickness function is a quadratic or an exponential function.
  • both the first and the second layer thickness profile function may be a quadratic or an exponential function. It may be that the second Schichtdickenverlaufsfunktion runs in opposite directions to the first Schichtdickenverlaufsfunktion, so that the period thickness varies less than the layer thickness of the more varying single layer.
  • the first layer group prefferably be the only layer group of the multilayer layer arrangement which is reflective for the EUV radiation.
  • the multilayer arrangement has, in addition to the first layer group, a second layer group with ten or more second layer pairs which is reflective for the radiation, the first layer group lying between the second layer group Substrate and the second layer group is arranged.
  • the second layer group is therefore located on the side of the first layer group facing away from the substrate, ie closer to the radiation entrance side of the multilayer layer arrangement.
  • the second layer group has at least ten second layer pairs.
  • the nominal layer thicknesses of the individual layers of the second layer group may be designed according to similar or different laws of formation than the nominal layer thicknesses of the first layer group.
  • the layer thicknesses of one of the layer materials can be defined as a function of the period number by a single-monotonous first layer thickness profile function and the layer thicknesses of the other of the layer materials vary depending on the period number according to a second layer thickness profile function.
  • more degrees of freedom result for the design in order to achieve a relatively homogeneous reflectivity.
  • the layer thicknesses of the first layer material and the second layer material vary in opposite directions linearly and the layer thicknesses of these layer materials also vary inversely within the second layer group, but optionally with different initial values and gradients.
  • the layer thicknesses of the first layer material and the second layer material vary in opposite directions linearly and the layer thicknesses of these layer materials also vary inversely within the second layer group, but optionally with different initial values and gradients.
  • a variation of layer thicknesses of the layer materials within the first layer group closer to the substrate is substantially stronger than within the second layer group closer to the radiation entrance side.
  • the variation of the layer thicknesses may be e.g. be at least twice as large or at least three times as large or at least four times as large as within the second layer group closer to the radiation entrance side.
  • the term "variation" here refers to the difference between the minimum and maximum layer thickness of a layer material within a layer group.
  • the nominal variation is equal to 0.
  • the layer thicknesses of the layer materials within the second layer group can thus be selected such that the second layer group provides a relatively large contribution to the maximum reflectivity of the multilayer layer arrangement, while the layer thicknesses in the vicinity of the substrate provide a favorable effect
  • one of the layer materials, in particular molybdenum has over the entire second layer a constant layer thickness
  • the layer thickness of the other layer material, in particular silicon within the second layer group is also constant, so that within the second layer group results in a layer structure similar to a "Monostack".
  • the invention also relates to an optical system with at least one EUV mirror of the type described above or below.
  • the optical system can be, for example, a projection objective or an illumination system for an EUV radiation microlithography projection exposure apparatus.
  • the EUV mirror may have a flat mirror surface or a convex or concave curved mirror surface.
  • the mirror at which the greatest incidence angle interval occurs can be constructed as described here, possibly also several or all EUV mirrors.
  • the EUV mirror can be a uniaxial or multiaxial tiltable individual mirror of a controllable multi-mirror array (MMA), at which different incidence angle intervals can occur depending on the tilt position.
  • MMA controllable multi-mirror array
  • a multi-mirror array may include multiple EUV mirrors of the type described herein. EUV mirrors can also be used in other optical systems, for example in the field of microscopy.
  • Fig. 1 shows a schematic vertical section through the layer structure of a
  • FIG. 2 is a layer thickness diagram of the first embodiment
  • Fig. 3 shows a layer thickness diagram of a second embodiment
  • Fig. 4 is a layer thickness diagram of a third embodiment
  • FIG 5 shows a comparison diagram of the angle of incidence dependence of the reflectivities of the first to third exemplary embodiments and of a reference mirror with a Mo / Si monostack (MS);
  • Fig. 6 is a layer thickness diagram of a fourth embodiment
  • Fig. 7 is a layer thickness diagram of a fifth embodiment
  • FIG. 8 shows a comparison diagram for the incidence angle dependence of the reflectivities of the fourth and fifth exemplary embodiments
  • FIG. 9 shows components of an EUV microlithography projection exposure apparatus according to an embodiment of the invention.
  • AOI Angle of Incidence
  • multi-layer mirrors having a multilayer multilayer arrangement which is reflective for the EUV radiation and which contains many pairs of layers (bilayers) comprising alternatingly applied layers of a layer material with a higher real part of the refractive index (also " Spacer ”) and a layer material with relatively lower real part of the refractive index (also called” absorber ").
  • Layer pairs can be constructed, for example, with the layer material combinations molybdenum / silicon (Mo / Si) and / or ruthenium / silicon (Ru / Si). In each case, silicon forms the spacer material, while Mo or Ru serve as the absorber material.
  • a layer pair may contain at least one further layer, in particular an intermediate barrier layer which may consist, for example, of C, B 4 C, Si x N y , SiC or of a composition with one of these materials and should prevent interdiffusion at the interface.
  • an intermediate barrier layer which may consist, for example, of C, B 4 C, Si x N y , SiC or of a composition with one of these materials and should prevent interdiffusion at the interface.
  • the embodiments illustrated below are intended to illustrate some basic principles.
  • the layer materials used in each case are molybdenum (Mo) and silicon (Si), resulting in a clear representation.
  • the basic principles can also be used at other wavelengths, other incidence angle intervals and / or other layer material combinations.
  • the basic principles also act independently of the use of barrier layers and / or protective layers, which may additionally be provided in a layer stack.
  • FIG. 1 shows a schematic vertical section through the layer structure of a multilayer laminate ML according to a first exemplary embodiment.
  • Fig. 2 shows an associated layer thickness diagram.
  • the abscissa gives the layer number LN of the individual layers and the ordinate their geometric layer thickness d in [nm].
  • the punctiform symbols represent single layers of molybdenum (Mo), while the triangular symbols represent single layers of silicon (Si).
  • the square symbols represent the (geometric) period thickness P of the layer pairs.
  • the substrate, not shown, is on the left side, so that the single layer with the layer number 1 directly adjacent to the substrate.
  • the radiation entrance side is correspondingly right at the highest layer number. This representation applies to all layer thickness diagrams of this application.
  • the EUV mirror of Fig. 1 or Fig. 2 has a substrate SUB, which has a substrate surface processed with optical precision, on which a multilayer coating ML is applied, which is also referred to below as "multilayer".
  • Layer arrangement in the example consists of 78 individual layers, alternating molybdenum layers (hatched) and silicon layers (without hatching), thereby forming 39 Mo / Si layer pairs, which are also referred to as Mo / Si bilayers or periods.
  • the multi-layer multilayer arrangement ML is essentially or exclusively formed by a first layer group LG1 which has a reflective effect on the incoming EUV radiation and has 39 first layer pairs, namely the 39 Mo / Si layer pairs.
  • the layer material silicon in this material pairing is the layer material with the higher real part of the refractive index, ie the relatively high refractive first layer material, while molybdenum has a relatively lower real part of the refractive index at the EUV wavelength and thus is the relatively low refractive second layer material.
  • the geometric layer thickness of an Si layer is denoted by d S i, the geometric layer thickness of the Mo monolayer by d Mo -
  • the sum of the geometric layer thicknesses of all individual layers of a layer pair is referred to here as the period thickness P, where the index i stands for the period number .
  • the periodic thickness also includes the geometric layer thicknesses of any further layers, for example diffusion-inhibiting intermediate layers whose layer thicknesses are generally several times lower than the layer thicknesses of Mo and Si.
  • the layer thickness of the Mo layers decreases continuously with increasing distance from the substrate in the direction of the radiation entrance side in accordance with a linear first layer thickness profile function.
  • Immediately adjacent Mo layers thus each have the same layer thickness difference from one another.
  • the individual layer thicknesses of the Si layers likewise decrease linearly from the substrate side to the radiation entrance side in equal steps, this dependence on the layer pair number being given by a linear second layer thickness progression function.
  • the layer thickness diagram in FIG. 2 illustrates this behavior.
  • the individual layer thicknesses of Mo and Si each vary linearly with the layer pair number. The same applies to the period thickness.
  • the layer thickness parameter a gives in each case an initial value of the layer thickness and Layer thickness parameter b the slope or the gradient of the layer thickness profile.
  • the layer thickness parameters the following applies:
  • the solid line labeled "1" shows the corresponding reflectivity curve in the first exemplary embodiment (FIGS. 1 and 2), ie with a linear decrease of the individual layer thicknesses of molybdenum and silicon between the substrate and the radiation entrance side 64%), however, the variation of the reflectivity over the angle of incidence range in the first embodiment is significantly lower than in the case of the pure monostack.
  • the linear layer thickness profile in the individual layers leads to a homogenization of the angle of incidence dependence of the reflectivity in the selected angle of incidence range for which the multilayer layer arrangement is designed.
  • a second exemplary embodiment is explained on the basis of the layer thickness profile diagram in FIG. 3, which shows a further reduced variation of the reflectivity within the selected angle of incidence range compared to the first exemplary embodiment, ie an improved broadband in the angular space.
  • the multi-layer arrangement has a total of 44 pairs of layers or periods, which are distributed over exactly two differently designed and stacked layer groups.
  • a first Layer group LG1 with 18 first layer pairs is arranged in the vicinity of the substrate.
  • a second layer group LG2 having a total of 26 second layer pairs is applied to this first layer group in such a way that the first layer group LG1 is arranged between the substrate and the second layer group LG2.
  • the geometric layer thickness of the monolayers decreases linearly from the substrate side to the radiation entrance side in accordance with a linear first layer thickness characteristic, while the layer thicknesses of the Si monolayers increase linearly from the substrate side to the radiation entrance side according to a linear second layer thickness progression function.
  • the second layer thickness profile function runs counter to the first layer thickness profile function.
  • the increase in the layer thicknesses of the Si layers is relatively stronger than the opposite decrease in the layer thicknesses of the Mo monolayers, so that the period thickness increases linearly from the substrate side to the radiation entrance side.
  • the decrease of the layer thicknesses of the Mo layers is relatively stronger than the opposite increase in the layer thicknesses of the Si layers, so that the period thickness from the side of the first layer group and the substrate side to the radiation entrance side, respectively, is slightly linear decreases.
  • the variation of layer thicknesses of the layer materials is more than four times as large within the first layer group LG1 as within the second layer group LG2.
  • the latter thus has a relatively highly reflective effect, similar to a "monostack", while the substrate-closer first layer group increases the broadband ratio.
  • Substrate-distant second layer group LG2 (1 ⁇ n ⁇ 26)
  • the multi-layer arrangement has only a single first layer group in which the layer thicknesses of all individual layers can be defined by simple monotone layer thickness profile functions.
  • the multilayer sandwich has 36 pairs of layers.
  • the single layer thicknesses for the Mo layers and the Si layers each vary according to an exponential layer thickness function, and the layer thicknesses of the Mo layers decrease exponentially from the substrate side to the radiation entrance side, while the layer thicknesses of the Si layers increase exponentially from the substrate side to the radiation entrance side.
  • the layer thickness profiles are chosen so that the period thickness first drops from the substrate side to the radiation entrance side and at a distance of a few pairs of layers to the radiation entrance side passes through a minimum, so that between this minimum and the radiation entrance side is a slight increase in the period thickness. This is mainly due to the fact that the layer thicknesses of the Si layers in the region of the radiation entrance side increase more than the layer thicknesses of the Mo monolayers fall in this section.
  • the layer thickness progression functions as a function of the layer pair number n (1 ⁇ n ⁇ 36) can each be defined by the following layer thickness parameters:
  • the angle of incidence dependence of the reflectivity of the third exemplary embodiment can be recognized by the dotted line labeled "3."
  • the reflectivity profile is very similar to that of the first exemplary embodiment, in which likewise only a first layer group is provided whose layer thicknesses follow a relatively simple systematic ,
  • the multi-layer arrangement here has only a single first layer group LG1 with 40 layer pairs.
  • the Mo layers have the same layer thickness, so that the layer thicknesses of the Mo layers can be defined by a very simple monotonous first layer thickness profile function, namely solely by specifying that constant layer thickness which applies to all Mo monolayers , Thus, only a single layer thickness parameter is necessary for the definition of all Mo layers.
  • the layer thicknesses of the other layer material, namely silicon vary depending on the period number according to a stochastic second Schichtdickenverlaufsfunktion.
  • the fluctuation range of the individual layer thicknesses around an average value is relatively large in the area close to the substrate, for example between the layer pair numbers 1 and 20 (ie individual layers deviate by more than 20% from the mean value) and decreases markedly in the direction of the radiation entrance side , so that, for example, in the last 10 Si layers in the vicinity of the radiation entrance side, the individual layer thicknesses only deviate by a maximum of 5% from a mean value related thereto.
  • the layer thicknesses of the individual silicon layers do not vary very greatly at the radiation entrance side.
  • a similar optical performance can be achieved if the fluctuation range of Si layer thicknesses in the region of the radiation entrance side is reduced to zero, so that not only the Mo layer thicknesses, but also the Si layer thicknesses in the substrate-distant region (in the second layer group) are constant.
  • 7 shows the layer thickness diagram of a corresponding fifth exemplary embodiment.
  • the multilayer layer arrangement can be subdivided into a first layer group LG1 close to the substrate and a second layer group LG2 remote from the substrate.
  • the layer thickness of the molybdenum monolayers is constant, while the layer thicknesses of the Si monolayers and thus also the periodic thicknesses vary randomly.
  • a second Layer group LG2 applied with a total of 20 pairs of layers.
  • the second layer group LG2 is constructed in the manner of a "monostack" in that both the Mo layer thicknesses and the Si layer thicknesses are constant in all second layer pairs.
  • Fig. 8 Similarities and differences in the reflectivity curves will be apparent from Fig. 8, in which the solid curve "4" shows the reflectivity curve of the fourth embodiment and the broken curve "5" shows the reflectivity curve of the fifth embodiment.
  • a maximum reflectivity of 64.7% is achieved at approximately 1 1 .5 ° incidence angle
  • the variation of the reflectivity in the considered angle of incidence range is approximately 4% -points (between approximately 64.7% and approximately 61 .5%). at 17.5 °).
  • a similar variation of the reflectivities results, whereby, however, the reflectivity level overall is lowered by approximately 0.3% -points compared to the fourth exemplary embodiment.
  • a two-part layer structure can be selected similar to the fifth embodiment, in which the substrate-distant second layer group LG2 can be produced more easily than in the case of the fourth embodiment due to the uniform layer thicknesses.
  • an intermediate layer can be arranged between the substrate and the substrate-next first layer pair of the first layer group, which in turn can be constructed from one or more individual layers.
  • Such intermediate layers may be provided, for example, for reducing stresses between the substrate and the reflective first layer group of the multi-layer layer arrangement.
  • a single-layer or multi-layer cap layer may be provided on the radiation entrance side to protect the multilayer protective device against oxidation and other harmful influences.
  • the cover layer may, for example, contain or be formed by a layer of ruthenium (Ru).
  • first layer group Some of the embodiments shown have exactly one layer group (first layer group), while others of the exemplary embodiments shown have exactly two layer groups (first and second layer group). It is also possible that a multilayer sandwich has more than two reflective layers, e.g. three or four layer groups or more, wherein at least one first layer group must be included, which has the described systematically simple layer thickness profiles.
  • a multilayer layer arrangement can have exactly three layer groups in which the layer thicknesses of the layer materials each have a linear layer thickness profile. function follow.
  • a multi-layer arrangement can not only have more than two (each reflective) layer groups, but also more than two (each reflective) layer groups, each with simple Schichtdickenverierin.
  • a variant of the example shown in FIG. 3 could be constructed such that ten or more of the periods on the radiation entrance side (eg layer numbers 60 to 90) are replaced by a "monostack" with a corresponding number of layer pairs with constant layer thicknesses of both layer materials ,
  • a first and a second layer group may be directly, i. without interposition of an intermediate layer, one another. It is also possible to arrange an intermediate layer between the first and the second layer group, which may consist of a single or a plurality of individual layers.
  • EUV levels of the type described in this application can be used in different optical systems, e.g. in the field of EUV microlithography.
  • FIG. 9 shows by way of example optical components of an EUV microlithography projection exposure apparatus WSC according to an embodiment of the invention.
  • the EUV microlithography projection exposure apparatus is used to expose a radiation-sensitive substrate W arranged in the region of an image plane IS of a projection objective PO with at least one image of a pattern of a reflective pattern generator or mask M arranged in the region of an object plane OS of the projection objective.
  • a Cartesian xyz coordinate system specified specified, from which the respective positional relationship of the components shown in the figures results.
  • the projection exposure machine WSC is of the scanner type.
  • the mask M and the substrate are synchronously moved in the y-direction during operation of the projection exposure apparatus and thereby scanned.
  • the system is operated with the radiation of a primary radiation source RS.
  • An illumination system I LL serves to receive the radiation of the primary radiation source and to form illumination radiation directed onto the pattern.
  • the projection objective PO is used to image the structure of the pattern onto a photosensitive substrate.
  • the primary radiation source RS may be, inter alia, a laser-plasma source or a gas-discharge source or a synchrotron-based radiation source.
  • Such radiation sources generate radiation RAD in the EUV range, in particular with wavelengths between 5 nm and 15 nm. In order for the illumination system and the projection objective to be able to work in this wavelength range, they are constructed with components that are reflective for EUV radiation.
  • the radiation RAD emanating from the radiation source RS is collected by means of a collector COL and directed into the illumination system I LL.
  • the illumination system comprises a mixing unit MIX, a telescope optics TEL and a field-shaping mirror FFM.
  • the illumination system forms the radiation and thus illuminates an illumination field which lies in the object plane OS of the projection objective PO or in its vicinity.
  • the shape and size of the illumination field thereby determine the shape and size of the object field OF which is actually used in the object plane OS.
  • a reflective reticle or another reflective pattern generating device is arranged during operation of the system.
  • the mixing unit MIX consists essentially of two facet mirrors FAC1, FAC2.
  • the first facet mirror FAC1 is arranged in a plane of the illumination system which is optically conjugate to the object plane OS. It is therefore also called a field facet mirror.
  • the second facet mirror FAC2 is arranged in a pupil plane of the illumination system, which is optically conjugate to a pupil plane of the projection objective. It is therefore also referred to as a pupil facet mirror.
  • the spatial (local) illumination intensity distribution at the field facet mirror FAC1 determines the local illumination intensity distribution in the object field.
  • the spatial (local) illumination intensity distribution at the pupil facet mirror FAC2 determines the illumination angle intensity distribution in the object field.
  • the projection objective PO serves to reduce the image of the pattern arranged in the object plane OS of the projection objective into the image plane IS which is optically conjugate to the object plane and lies parallel to it.
  • This mapping is done by means of electromagnetic Radiation from the extreme ultraviolet (EUV) range by an operating wavelength ⁇ , which in the example is 13.5 nm.
  • EUV extreme ultraviolet
  • the projection objective has six mirrors M1 to M6 with mirror surfaces which are arranged in a projection beam path PR between the object plane OS and the image plane IS in such a way that a pattern arranged in the object plane or in the object field OF is mirrored into the image plane or mirrors by the mirrors M1 to M6 the image field IF is reproducible.
  • the mirrors M1 to M6 each have curved mirror surfaces, so that each of the mirrors contributes to the imaging.
  • the beams of the projection beam path coming from the object field OF initially fall on the slightly convexly curved first mirror M1, which reflects the beams to the slightly concave second mirror M2.
  • This reflects the rays to the convex third mirror M3, which deflects the rays laterally to the concave mirror M4.
  • the latter reflects the rays on the fifth mirror M5 arranged geometrically close to the image plane, which has a slightly convexly curved mirror surface and reflects the rays to the large concave mirror M6, which is the last mirror in front of the image plane and the rays in the direction of the image field IF focused.
  • the projection lens consists of two partial lenses.
  • the first four mirrors M 1 to M 4 form a first partial objective which generates an intermediate image IMI in the beam path between the fourth mirror M 4 and the fifth mirror M 5.
  • the intermediate image lies in an intermediate image plane, which is optically conjugate to the object plane and to the image plane.
  • Geometrically, the intermediate image is arranged next to the sixth mirror M6.
  • the second partial objective which consists of the fifth and the sixth mirror, images the intermediate image reduced to the image plane.
  • At least one of the mirrors M1 to M6 may have a layer structure according to an embodiment of the invention.
  • a reflective coating having a broadband effect in the angular space can be favorable. It is also possible to design a plurality or all mirrors M1 to M6 according to an embodiment of the invention.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Optical Elements Other Than Lenses (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
  • Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)

Abstract

L'invention concerne un miroir EUV qui comprend un substrat (SUB) et un ensemble multicouches (ML), déposé sur le substrat, qui a une action réfléchissante vis-à-vis d'un rayonnement de longueur d'onde λ de la gamme des ultraviolets extrêmes (EUV) et qui comporte un grand nombre de paires de couches alternées en une matière à indice de réfraction élevé et une matière à indice de réfraction faible, la matière à indice de réfraction élevé ayant pour la longueur d'onde une composante réelle de l'indice de réfraction qui est supérieure à celle de la matière à indice de réfraction faible. L'ensemble multicouches comprend un premier groupe de couches (LG1) ayant une action réfléchissante vis-à-vis du rayonnement et comportant dix premières paires de couches ou plus, chaque première paire de couches comportant une première couche (H) constituée d'une première matière à indice de réfraction élevé et ayant une première épaisseur, une deuxième couche (L) constituée d'une deuxième matière à faible indice de réfraction et ayant une deuxième épaisseur et une épaisseur périodique (P) qui correspond à la somme des épaisseurs de toutes les couches d'une première paire de couches. Les épaisseurs d'une des matières de couche peuvent être définies en fonction du nombre de périodes par une première fonction de profil d'épaisseur de couche simplement monotone, par exemple par une fonction de profil d'épaisseur de couche linéaire, quadratique ou exponentielle. Les épaisseurs de l'autre des matières de couche varient en fonction du nombre de périodes selon une deuxième fonction de profil d'épaisseur de couche.
PCT/EP2015/050687 2014-01-20 2015-01-15 Miroir euv et système optique à miroir euv WO2015107116A1 (fr)

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JP2016564397A JP6527883B2 (ja) 2014-01-20 2015-01-15 Ｅｕｖミラー及びｅｕｖミラーを備えた光学系
US15/215,123 US10203435B2 (en) 2014-01-20 2016-07-20 EUV mirror and optical system comprising EUV mirror

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JP6736763B2 (ja) * 2017-03-31 2020-08-05 東洋紡フイルムソリューション株式会社 多層積層フィルム
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US11448970B2 (en) * 2020-09-09 2022-09-20 Taiwan Semiconductor Manufacturing Co., Ltd. Lithography system and methods

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DE102014200932A1 (de) 2015-07-23

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